1. Field of the Invention
The present invention relates to a collision prevention device of a measurer. More specifically, the present invention relates to a collision prevention device of a measurer measuring dimensions or the like of a measured object while relatively displacing the measured object and a non-contact probe.
2. Description of Related Art
A known example of a measurer using a non-contact probe is a coordinate image measurement device capable of displacing a measured object or a non-contact probe in mutually orthogonal X, Y, and Z axis directions and of measuring dimensions or the like of the measured object based on an image acquired by the non-contact probe.
In the coordinate image measurement device of this kind, the non-contact probe is used at a position adjacent to the measured object. In particular, during measurement, the non-contact probe is displaced in three-dimensional directions relative to the measured object. At this point, the non-contact probe may collide with the measured object due to operator inattention, a mistaken setting for coordinates input to a computer, or the like.
In order to prevent damage to the non-contact probe, measurement device main body, measured object, and the like due to such a collision, a collision prevention device for a measurer has been proposed (Japanese Patent Publication No. 3831561). In the collision prevention device described by Japanese Patent Publication No. 3831561, a ring-shaped collision detector is provided covering a non-contact probe, and when the collision detector is displaced relative to the non-contact probe, the relative displacement is detected and a command is given to stop displacement or to retreat.
In order to make the collision prevention device described in Japanese Patent Publication No. 3831561 effective at preventing collisions in any direction of three-dimensional displacement, the ring-shaped collision detector covering an outer circumference of the non-contact probe is used. However, under the following conditions, the collision prevention device according to Japanese Patent Publication No. 3831561 may not be fully effective.
First, in a case where an operation portion is provided to a surface of the probe and an operator operates the operation portion. With the above-described collision prevention device, the ring-shaped collision detector may obscure the operation portion and prevent the operator from operating the operation portion on such a probe.
Second, in a case where a measured surface of the measured object is flat and includes no height-direction unevenness. With such a measured object, there is no risk of collision when displacing in the X axis direction and Y axis direction (both directions lying along the measured surface). Preventing collisions in the Z axis direction only is sufficient. However, the above-described collision prevention device uses the ring-shaped collision detector which encompasses a Z axis area. This configuration is excessive.
Third, in a case where a Z axis direction working distance of the probe is extremely small. With the above-described collision prevention device, a certain displacement distance is required in order to respond to contact. In addition, even when a portion of the ring-shaped collision detector makes contact with the flat surface of the measured object while displacing in the Z axis direction, in some cases the contact cannot be detected until there is further displacement in the Z axis direction and a majority of the ring-shaped collision detector makes contact, and the displacement cannot be safely stopped.